Multiple people familiar with the punishment told AP on Thursday about Keselowski's fine. The people spoke on condition of anonymity because NASCAR did not publicize the fine.

Keselowski

NASCAR has been privately punishing drivers for making disparaging remarks about the series over the last two years.

The fine is believed to be $25,000.

"We're not doing this because it's better for the teams," Keselowski said last week during an appearance at the NASCAR Hall of Fame . "I don't think we're really going to save any gas. It's a media circus, trying to make you guys happy so you write good stories. It gives them something to promote. We're always looking for something to promote, but the honest answer is it does nothing for the sport except cost the team owners money.

"Cars on the street are injected with real electronics, not a throttle body (like in NASCAR). So we've managed to go from 50-year-old technology to 35-year-old technology. I don't see what the big deal is."

NASCAR has called the move to electronic fuel injection part of its green initiative and said engines should run more efficiently by controlling the fuel mixture through electronics.

NASCAR spokesman Kerry Tharp acknowledged there had been conversations with Keselowski.

"We did talk to Brad following his recent comments that were highly critical of the series moving to electronic fuel injection next season," Tharp said. "We made it clear to him that these kind of comments are detrimental to the sport, and we handled it accordingly with him."

In the past NASCAR has quietly fined Ryan Newman for criticizing racing at Talladega and Denny Hamlin for posts he made on Twitter.

Earlier this year, Newman was fined $50,000 for an incident with Juan Pablo Montoya. NASCAR has refused to discuss the fine or what happened with Montoya to earn Newman the penalty.